I Use the 1Mobile store app, just download and install from their webpage. Almost all apps are available ( at least I haven't come across one that isn't).

The best part of 10.3.1 on the classic is the integration of android app with BB10 OS. The most important one for me is the integration while "sharing" content from an android app. On the earlier version sharing was limited to very few apps. Now though, it is complete integration. Great work by developers at BlackBerry